Piston-ring packings, more particularly for high pressure



June 5, 1956 J. KRUGER 2,749,195

PISTON-RING PACKINGS, MORE PARTICULARLY FOR HIGH PRESSURE Filed Dec. v, 1953 ZHIIMHIHIIIMIZZU v y 2,749,195 lcfi Fatented June 5, 1956 PISTON-RIN G PACKINGS, MORE PARTICULARLY FOR HIGH PRESSURE Joachim Kriiger, Lubeck-Schiutup, Germany, assignor to Liibecker Kaltemaschinen-G. m. b. H., Lubeck- Schlutup, Germany Application December 7, 1953, Serial No. 396,523

Claims priority, application Germany December 6, 1952 5 Claims. (Cl. 309--31t) This invention relates to a piston-ring packing for pistons and piston rods with reciprocating and rotary motion, and more especially to piston-ring packings of the kind in which a packet of slotted annular laminations, bearing against one another in a guiding groove of a sliding body, is pressed radially against a guide surface by the working pressure, with the interposition of a resiliently sealing annular body.

Such laminated packings pressed by the working pressure against a guide face have yielded satisfactory sealing results at moderate pressures when the annular laminations, lightly gripped together at a certain periphery, could collectively bear snugly against the guide surface, and a certain oil film prevented the direct access of the compression pressure to the guiding surface. At higher working pressures, however, it has been ascertained that the protection afforded by this oil film is no longer adequate to exclude effectively the action of the working pressure between the sliding body and the cylindrical guiding surface from the place where the packet of laminations is located.

It has now been found that the working pressure in an outward direction brought into action upon the packet of laminations by way of known ducts in the interior of the sliding body, in consequence of the frictional losses in the packet of laminations, and also in consequence of the reduction in internal pressure in the annular sealing body, undergoes an appreciable weakening of its effect.

Accordingly the operating pressure might come into action unhindered in the annular gap between the sliding body and the guide surface at the first annular lamination of the packet of laminations.

Any incomplete bearing of a part of the annular surface of the first ring on the guide surface results, as experiments have shown, in the full operating pressure brought into existence here being able to interpose itself in the annular gap, and being now capable of overcoming the restricted internal application pressure. As soon as the first annular lamination is hereby held back from applying its pressure, the same series of operations can start with the next annular laminations.

At high pressures there is accordingly a diminution of the sealing power of such packets. In particular this occurs when certain tiltings of the sliding body, and therefore of the guidance of the annular laminations occur in operation, if the individual annular laminations are impaired in their radial movability by friction against one another.

According to the invention, therefore, these ascertained defects for high operating pressures are precluded by providing additional means by which the application pressure of the annular laminations against the operating guide surface is maintained higher than the fluid pressure on the guidesurface to be sealed.

Such means may either act additively to the operating pressure coming into action from within, or may act by means that reduce the eifective pressure of the operative pressure on the packet of laminations in the annular gap between the sliding body and the guide surface.

According to a further feature of the invention it is proposed for the first case to let the split rings of the packet of annular laminations bear with a substantial initial stress of their own, even without any operative fluid pressure, against the guide surface in the pressure seat.

The same additive effect is also obtained if the resiliently sealing annular body bears against the internal surface of the packet of annular laminations with a considerable initial stress. 1

If an internal stress in the resiliently sealing annular body is not attainable to a substantial extent on material grounds, it is further suggested, on the internal annular surface of the resiliently sealing annular body, to locate a leaf-spring ring pressing radially outwards, the known inlet ducts and valve devices in the interior of the sliding body then supplying the operating pressure to the internal annular surface of the leaf-spring ring.

In order to enable a uniform additional stress to be given in the case of all the individual rings of the packet of laminations, it is advisable to make such a leaf-spring ring approximately as wide as the packet of laminations.

It is also to be borne in mind that the pre-stressing leafspring ring should be secured against lateral displacement between the radial boundary planes of the packet of laminations. For this purpose, it may be guided by a supporting ring, which at the same time carries the resiliently sealing annular body.

If such a leaf-spring ring is selected as a supplementary stressing means for the radial pressing of the packet of laminations, it is advisable to let the known ducts provided in the interior of the sliding body, which serve for transmitting the operating fluid pressure, open into an annular gap underneath the internal annular surface of the leaf-spring ring For the second method of providing a difference between application pressure and operating pressure in the annular gap it is proposed to provide, between the compression space and the packet of laminations, one or more piston rings lodged singly in separate annular grooves in the sliding body, which are constructed as split piston rings of the usual breadth, and are preferably made of hard cast iron.

Such an individual piston ring, or, better still, each of such piston rings, opposes a substantial throttling action, in the event of incomplete sealing contact, to the penetration of the operating pressure into the annular gap between the sliding body and the guide surface.

If more than one piston ring is employed, there is also added the labyrinth effect, and the reduction of pressure, by expansion, beyond a passage through a gap.

The very favourable result is hereby attained that at the first annular lamination of the packet it is not the full compression pressure that comes into action, particularly in the case of high operating pressures, whereas the operating pressure coming into action unhindered in an outward direction upon the packet of laminations through the internal ducts is sufficient, notwithstanding any frictional losses, or losses conditioned by material, to press each individual annular lamination with greater pressure against the guide surface.

Obviously the additive means for increasing the application pressure may be adopted, individually or collectively, or may even be adopted jointly with the subtractive means acting upon the annular-gap pressure.

For all these combinations it is however important to smooth the lateral annular faces of the laminations flat in a radial plane, so as to prevent losses of pressure occurring owing to friction of the annular laminations against one another.

It has also been found advantageous, for the purpose of securing radial mobility and to prevent canting of the laminations relatively to one another, to guide the packet of laminations in the internal annular groove of the sliding body in a radial plane between two wider split piston rings, as the tilting that may have to be feared in the operation of a rapidly reciprocating sliding body is just what would prove unfavourable to the individual mobility of the laminations in the event of no;irauial guidance of the packet.

The above suggestion of providing, between the packet of laminations to be sealed and the compression space, one or more piston rings, has also proved extremely val uable for the purpose of counteracting such a tilting of the sliding body in operation.

Even when the packet of laminations, which in itself is radially movable, is of great breadth, the sliding body does not always find reliable bearing in the guiding cylinder, particularly when non-axial working members, such as a connecting-rod, are directly attached to the piston. In such cases the simple piston rings arranged in the annular gap to reduce the fluid pressure therein, cooperate advantageously with the packet of laminations, to provide reliable additional axial guidance of the sliding body.

The present construction has proved exceedingly advantageous for high-pressure pumps in refrigerating plant and in the high compression of gases, but can likewise be advantageously adopted in reciprocating engines.

When working with hot compression gases, the resiliently sealing annular body should be a narrow ring of a resilient metal.

Similarly, since it is advantageous to arrange the pressure-diminishing and guiding piston rings between the compression space and the packet of laminations, it is of importance on operational grounds to lodge, upon the sliding body, in an annular groove beyond the sealing surface of the packet of laminations as seen from the compression space, at least one resilient stripping or wiping ring, preferably being made of rubber-lilte material.

Such stripping rings are advantageous for the purpose of preventing oil and dirt coming to the packet of laminations from the crank casing for instance, and possibly impairing the free mobility of the laminatiens and their contact position. It has furthermore been found that such stripping rings, constructed as leather or rubber sleeves, if they are lodged with sufiicient excess of material in the grooves, are useful as smoothing means to facilitate the original introduction of the sliding body into the guide cylinder.

In the accompanying drawings two piston constructions are illustrated, but the invention is not limited to the details of the embodiments illustrated. For instance, by reversing the location of the packet of laminations in a bore in the body, a piston-rod packing can obviously be constructed in the same manner.

Figure 1 shows a section through a piston, wherein additive tensioning or stressing means are adopted; and

Figure 2 shows a piston in which the pressure difference upon the applying surface is obtained substantially by subtractively acting means.

Figure 1 shows a piston body or piston head 2 slidable in a bore 1. In an annular groove 3 in this sliding body 2 is lodged, between two relatively thick slotted piston rings 4, 4, a packet of laminations consisting of a number of narrow annular laminations 5.

The thick piston rings 4 and the annular laminations S in the groove 3 rest with their internal annular surfaces upon a resiliently sealing annular body 6, which, as a rubber-like U-shaped bead ring, engages with dovetailed U-limbs 7, 7 behind a likewise dovetail-shaped supporting ring 8. This supporting ring 3 is secured to the base of the piston groove 3.

If the piston is to be employed in refrigerating apparatus for the compression of carbon dioxide, a chemically inert material must as far as possible be selected for the resiliently sealing annular body 6.

in a guiding groove in the supporting ring 8 a leafspring ring 9 of o'ilproof, gas-proof and acid-proof resilient material bears outwards with initial stress against the web of the resiliently sealing annular body 6.

This initial stress of the leaf-spring ring 9 should be so great that it is capable of overcoming the resilience of the annular body 6 to such an extent as to transmit to the packet of laminations 5, 5 located behind it a sufficiently uniform initial stress for the individual laminations 5. The guiding groove in which the leaf-spring ring 9 is lodged in the supporting ring 8 is so held that in any condition of stress there remains an annular gap between the internal surface of the leaf-spring ring 9 and the base of the guiding groove in the supporting ring 8. Into this annular gap there opens a duct 10, which passes through the supporting ring 8.

This duct is in open communication with a further duct 11 and auxiliary control members 12, and allows working pressure from the cylinder space 1 to enter this annular gap. The gaseous or other fluid pressure supto the annular gap is now able to act with the full sing pressure upon the internal surface of the leafspring ring 9, and to transmit this working pressure rc- Eiably through the medium of the resilient annular body 6 to the packet of laminations 5, 5, uniformly over the whole breadth of the packet.

Obviously the thicker piston rings 4, which are located beside the packet of laminations 5, 5, are also acted upon to a certain extent by the internal working pressure through the medium of the resiliently sealing annular body 6, but a very important concentration of the transmission or" the working pressure to the packet of laminations 5, 5 between the radial boundary planes of the packet of laminations is ensured by the guidance of the leaf-spring ring.

The leaf-spring 9, thus pre-stressing the packet of laminations 5, 5, may be constructed as a single-layer spring ring, with overlapping ends if desired.

In view of the sensitiveness of the resilient annular body on which the leaf-spring 9 bears, care must be taken to ODVltltC sharp corners and edges.

it is very important that the individual annular laminations 5, and likewise the thicker rings 4, which bear with their lateral surfaces against one another or against the walls of the groove 3, should be very carefully prepared as sliding surfaces, preferably ground and lapped. it is only in this way that the radial mobility of the laminations 5 and of the piston rings 4 in a direction perpendicular to the sliding surface is ensured.

Such a measure ensures reliable contact of the sliding surfaces, and a reduction of the working pressure brought into action from the interior.

Upon the sliding body 2 in Figure 1, beyond the sealing surface of the packet of laminations 5 as seen from the cylinder space 1, there is furthermore introduced a resilient stripping or wiping ring 13 in a separate groove. in the present case this stripping ring is constructed as a known leather or rubber sleeve. Such a sleeve 13 takes over: the initial scaling in a newly manufactured compression cylinder 1 when a pump comprising such a unit is being run in, and renders the original high compression it wears away very quickly in a known manner or the margins of the lips. in the meantime. however, the laminated pa king effects a very fine grinding or polishing of the cylinder walls, and thus attains maximum fiuidtightness owing to the now more advantageous be; ng of the annular laminations 5. After the first Wearing of the margins of the lips of the sleeve 13 during operation, this pt king ever, in a more advantageous form, the stripping of particles of oil and dirt,

which are usually sprayed on out of the connecting-rod space, and thereby keeps the rubbing surfaces of the laminations free from the action of these particles.

In Figure 2, in a similar piston bore 21, a differently constructed sliding body 22 is slidably lodged. In an undercut or dovetail-shaped groove 23 turned in the repeatedly offset machined piston head of the sliding body 22, a sleeve of resilient material is inserted as an annular body 26 sealing from the interior. Over this annular body 26, as in the case of the piston of Figure 1, are mounted first a relatively thick piston ring 24, then a plurality of annular laminations 25, and to conclude, another relatively thick piston ring 24.

By means of a screw ring 42 mounted upon the piston head of the sliding body'22 and exhibiting a turned undercut or dovetail-shaped groove 43 corresponding to the dovetail-shaped groove 23, the annular sealing body 26 is resiliently pre-stressed, and at the same time the thick piston rings 24, with the packet of laminations 25, are gripped together for slidable bearing against one another.

One or more ducts 31 through the sliding body 22 transmit the Working pressure in the piston space 21 by way of known control members 32 to a location beneath the internal annular surface of the resilient annular body 26, so that the gaseous or other fluid pressure, thanks to the pressure in the undercut grooves 23 and 43, can be transmitted by the annular body 26 to the packet of laminations 25 and likewise to the thick piston rings 24.

In order to keep the rubbing surfaces of the packet of laminations 25 free from particles of oil and dirt from the connecting-rod space, two stripping rings 33 are lodged, in the example illustrated in Figure 2, in separate grooves towards the connecting-rod end of the sliding body 22.

It is important, however, in the embodiment illustrated in Figure 2, that the packet of laminations 25 should be preceded, in the direction towards the cylinder space 21, by ordinary split piston rings 41 in separate annular grooves. These rings on the one hand prevent the full working pressure of the cylinder space 21 in the annular gap between the sliding body and the guiding surface of the cylinder from reaching the packet of laminations 25, and on the other hand, these piston rings provide a supplementary guidance for the sliding body 22, which is otherwise guided only upon the sliding surface of the laminations 25. Any tilting or unsteadiness of the sliding body 22 in the piston space 21 is thereby most advantageously prevented- I claim:

1. A piston comprising a piston body and a piston ring groove, a plurality of split annular rings laminated in said body, said rings having flat smooth sides and being radially movable with respect to each other to make contact with a cylinder wall, duct means for transmitting only the highest cylinder pressure to beneath said rings for urging said rings radially outward, and hard cast iron piston ring means between said plurality of rings and the piston head for reducing the cylinder pressure between the ring means and the plurality of rings to a value below the pressure applied beneath said plurality of rings.

2. A piston as in claim 1, said hard cast iron ring means further comprising a plurality of piston rings spaced from each other and seated in individual piston ring grooves.

3. A piston as in claim 1, further comprising a relatively wide split piston ring mounted in said wide piston ring groove at each end of said plurality of laminated rings and forming radial guide means therefor.

4. A piston as in claim 1, further comprising a resilient stripping ring mounted on said piston body rearwardly of said plurality of laminated rings.

5. A piston as in claim 1, said duct means further comprising a resilient annular sealing body in said wide groove beneath said plurality of laminated rings composed of a thin metal spring.

References Cited in the file of this patent UNITED STATES PATENTS 157,888 Taylor 1. Dec. 15, 1874 632,441 Byle et a1. Sept. 5, 1899 1,284,341 Honegger Nov. 12, 1918 1,464,223 Sleicher Aug. 7, 1923 

